CN113445972A

CN113445972A - Method and system for determining zonal water injection testing and regulating period of tight oil reservoir

Info

Publication number: CN113445972A
Application number: CN202110932795.XA
Authority: CN
Inventors: 王瑞; 程嘉瑞; 张明; 韩继勇; 孙娜娜; 李震宇; 车杰; 惠海伟
Original assignee: Xian Shiyou University
Current assignee: Xian Shiyou University
Priority date: 2021-08-13
Filing date: 2021-08-13
Publication date: 2021-09-28

Abstract

A method and system for determining a period for measuring and adjusting layered water injection in a tight oil reservoir, comprising the following steps: establishing a layered water injection multi-layer node analysis model; The search method is used to solve the problem; through the multi-layer node analysis model of layered water injection, the injection pressure and actual injection volume of the two layers under this working condition are obtained, and then according to the definition of the injection error of a single well, the design injection volume-actual injection volume/ Design the injection volume and predict the injection error; according to the decreasing trend of the formation pressure with time, it is substituted into the multi-layer node analysis model of layered water injection, and the variation trend of the injection pressure and the actual injection volume of the two layers with time is obtained. Quantitative requirements are compared to predict the cycle of dispensing inspection and adjustment. The invention provides a corresponding theoretical basis for clarifying the characteristics and laws of stratified water injection in low-permeability oil reservoirs, and improving the effect of the injection process, and can predict the allocation error of stratified water injection, the qualified rate of allocation and injection, and the measurement and adjustment period. Effectively guide the practice of layered water injection technology and improve water injection benefits.

Description

Method and system for determining zonal water injection testing and regulating period of tight oil reservoir

Technical Field

The invention belongs to the technical field of petroleum engineering, and particularly relates to a method and a system for determining a layered water injection testing and regulating period of a tight oil reservoir.

Background

At present, the domestic stratified injection technology goes through fixed type separate injection, steel wire throwing and fishing type separate injection and cable testing and adjusting type separate injection and enters the fourth stage of intelligent separate injection, namely, under the development trend that equipment and tools are intelligentized, how to effectively use the tools aiming at water injection development is really and efficiently, the theoretical research of a pressure system of a stratified injection and production well matched with the tools is critical, and the first core problem is the determination of separate injection and injection allocation quantity. The contents related to the multi-layer multidirectional injection quantity and yield splitting technology in the latest fine water injection optimization research by utilizing big data and artificial intelligence analysis are also disclosed.

The determination method of the injection allocation amount of the zonal injection comprises a single-factor effective thickness method (H) and a formation coefficient method (KH) based on static parameters, a multi-factor split coefficient method based on production dynamics, a displacement characterization-based method and a zonal injection pressure system analysis method. Among the methods based on pressure system analysis are separate injection node analysis, complete reservoir numerical simulation, and pipe flow and seepage coupling. The node analysis method is based on the principle of conservation of mass and momentum of outflow and inflow nodes, and is simple and practical compared with other methods. The application research of node analysis in water injection process and separated layer water injection process is less at home and abroad.

The compact oil reservoir has bright water injection development characteristics, namely strong heterogeneity and large difference of water absorption between layers and in layers; and secondly, the single well and single layer water injection amount is small, and the dispensing manual or underground automatic test and allocation difficulty is high. In order to further improve the dispensing development effect, studies on dispensing injection errors and dispensing modulation cycle predictions are required.

Disclosure of Invention

The invention aims to provide a method and a system for determining a zonal water injection testing and regulating period of a tight oil reservoir, which solve the problems in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for determining a zonal water injection testing and regulating period of a tight oil reservoir comprises the following steps:

establishing a layered water injection multi-layer node analysis model on the basis of the single-layer general water injection node model;

solving the layered water injection multi-layer node analysis model until the inflow and outflow pressure difference at the bottom hole node meets the maximum value required by the inflow and outflow pressure difference of the first layer bottom hole node;

obtaining two-layer injection pressure and actual injection quantity under the working condition through a layered water injection multi-layer node analysis model, designing injection quantity-actual injection quantity/designed injection quantity according to the definition of single well injection distribution error, and predicting the injection distribution error;

and substituting the ground pressure into a layered water injection multilayer node analysis model according to the descending trend of the ground pressure along with time to obtain the change trend of the two-layer injection pressure and the actual injection amount along with time, comparing the change trend with the injection allocation requirement, and predicting the injection allocation measuring and adjusting period.

Further, in the single-layer general water injection well node analysis, the division of the pressure drop system comprises: pressure drop Deltap of ground horizontal pipe₁Pressure drop Δ p of underground vertical pipe₂Pressure drop Δ p of the mouth flow₃And the pressure drop Δ p of the injection water in the ground₄Four parts(ii) a The pipe flow pressure drop is calculated by a Darcy formula, the nozzle flow pressure drop is calculated by a nozzle flow pressure drop model, and the seepage flow pressure drop of the injected water in the ground is calculated by a plane radial flow pressure drop model; the pressure drop system division of the layered water injection well node model is characterized in that the flow pressure drop of a shaft pipe, the flow pressure drop of a nozzle and the seepage pressure drop are divided into a plurality of parts according to a plurality of layers, wherein the parts are respectively delta p_2-1、…、△p_2-m，△p_3-1、…、△p_3-m，△p_4-1、△p_4-mM is the number of layers of the stratified water injection;

further, the specific formula of the pressure drop of each part is as follows:

wherein Q is the amount of injected water, m³/d；L_pIs the ground pipeline length, m; d_pIs the ground pipeline inner diameter, m; a. the_pIs the internal cross-sectional area of the ground pipeline, m²；

In the formula, L_w、H_wWell depth and vertical depth, m, respectively; d_wIs the inner diameter of the oil pipe, m; a. the_wIs the internal cross-sectional area of the oil pipe, m²；λ_p、λ_wThe coefficients of flow friction resistance in the ground pipeline and the oil pipe are respectively, and the method is dimensionless; subscripts 1, m refer to the first and mth layers, respectively, m ═ 1, 2, …, m_max；m_maxThe maximum number of layers is injected by layers without dimension;

in the formula D_nThe inner diameter of the water distribution nozzle is m; a. the_nFor the overflow area of the water distribution nozzle, the overflow area m of a water nozzle with adjustable flavor, such as a U-shaped throttle orifice²；C_dFor adjusting the flow coefficient of the tap, C_d(x)＝-3.1004x⁴+8.7432x³-8.8037x²+3.64x +0.2635, dimensionless; x is the opening degree of the water nozzle, 0-1.0 and is dimensionless;

in the formula, h is the effective thickness of the reservoir, m; k_wIs water phase permeability, μm²；r_wIs the wellbore radius, m; r is_eThe water injection wave radius is m; s is epidermal factor, and is dimensionless; rho_wAs density of the aqueous phase, kg/m 3; mu.s_wIs the aqueous phase viscosity, mPa.s; b is_wIs the volume coefficient of the water phase and is dimensionless;

establishing a layered water injection node analysis model, taking the bottom hole flow pressure of the 1 st layer as a solution point, and using an inflow dynamic equation as shown in the formula, a layer 1 outflow dynamic equation and the 2 nd to m th layers_maxThe layer outflow dynamic equation and the relation among the injection quantities of the multiple layers form a node analysis model of the multiple-layer injection water injection well, and the node analysis model is shown as a formula (5);

in the formula, p_jwf-inIs the bottom hole pressure of the inflow node, Pa; p is a radical of_jwf-outIs the bottom hole pressure of the outflow node, Pa; p is a radical of_rIs the formation pressure, MPa.

Furthermore, a stepwise searching method in a nonlinear equation set numerical solution method is adopted for solving, and a split coefficient (the ratio of the upper injection flow to the total injection flow) r of the injection allocation amount is firstly assumed_sfjAnd the total injection quantity Q is the value rsfj epsilon (0, 1), and Q epsilon [0,1600]Then substituting into the upper layer outflow dynamic equation to calculate to obtain the total injection quantity and Q, and the upper layer injection quantity Q₁And injection pressure p_jwf1Then substituting the lower layer outflow dynamic equation to obtain the lower layer injection quantity Q₂And injection pressure p_jwf2Trial calculation and search are conducted one by one from small to large until the inflow pressure difference and the outflow pressure difference at the bottom hole node meet the requirement epsilon, and the calculation model is shown as a formula (6);

in the formula, Q_jM is the total dosage³/d；r_sf-mThe split coefficient of the injection quantity is distributed for the mth layer, and the dimension is not needed; epsilon is the maximum value of the inflow pressure difference and the outflow pressure difference of the bottom hole node of the first layer, and is MPa.

Further, the dispensing error is expressed as follows:

E_Q＝[Q(t₂)-Q(t₁)]/Q(t₁) (7)

if only the formation pressure changes at two times, then there are:

[Q，Q₁，…，Q_m，p_jwf1，…，p_jwfm](t)＝f_w[ (fluid Property: p)_w,B_w,μ_w) (ground line: L)_p,ε_p,D_p) (wellbore 1: L)_w1,H_w1,ε_w,D_w,r_w) (wellbore 2: L)_w2,H_w2…, (shaft m: L)_wm,H_wm(water distribution nozzle 1: 2R)_n1,h_n1+2R_n1,x_n1) (water distribution nozzle 2: 2R)_n2,h_n2+2R_n2,x_n2) …, (water distribution nozzle m: 2R)_nm,h_nm+2R_nm,x_n2) (reservoir 1: h)₁,r_e1,p_r1(t),K_w1,s₁,p_ffB (reservoir 2: h)₂,r_e2,p_r2(t),K_w2,s₂) …, (reservoir m: h)_m,r_em,p_rm(t),K_wm,s_m) (Water injection Process: p)_j,Q_max)]；(8)

The calculation formula of the corresponding injection allocation qualified rate is as follows:

R_Q＝1-E_Q (9)。

further, the measured and adjusted period is defined as the time interval when the error of the two measured and adjusted injections is larger than the requirement, and the expression is as follows:

CY_Q＝t_n-t₁when E is_Q＝[Q(t_n)-Q(t₁)]/Q(t₁)＜E_{Q requirement}Then, n is 2,3, 4. (10)

[Q，Q₁，…，Q_m，p_jwf1，…，p_jwfm](t)＝f_z[ (fluid Property: p)_w,B_w,μ_w) (ground line: L)_p,ε_p,D_p) (wellbore 1: L)_w1,H_w1,ε_w,D_w,r_w) (wellbore 2: L)_w2,H_w2…, (shaft m: L)_wm,H_wm(water distribution nozzle 1: 2R)_n1,h_n1+2R_n1,x_n1) (water distribution nozzle 2: 2R)_n2,h_n2+2R_n2,x_n2) …, (water distribution nozzle m: 2R)_nm,h_nm+2R_nm,x_n2) (reservoir 1: h)₁,r_e1,p_r1(t),K_w1,s₁,p_ffB (reservoir 2: h)₂,r_e2,p_r2(t),K_w2,s₂) …, (reservoir m: h)_m,r_em,p_rm(t),K_wm,s_m) (Water injection Process: p)_j,Q_max)])]；(11)。

Further, the design dosage is the last measured dosage; the actual dispensing amount is the dispensing amount measured at the next time.

Further, a tight oil reservoir zonal injection testing and adjusting period determining system includes:

the model establishing module is used for establishing a layered water injection multi-layer node analysis model on the basis of the single-layer general water injection node model;

the solving module is used for solving the layered water injection multi-layer node analysis model until the inflow and outflow pressure difference at the bottom hole node meets the maximum value required by the inflow and outflow pressure difference at the bottom hole node of the first layer;

the injection allocation error prediction module is used for obtaining two-layer injection pressure and actual injection amount under the working condition through a layered water injection multi-layer node analysis model, designing injection allocation amount-actual injection allocation amount/designed injection allocation amount according to the definition of single well injection allocation error, and predicting the injection allocation error;

and the injection allocation measuring and adjusting period prediction module is used for substituting the layered water injection multi-layer node analysis model according to the descending trend of the formation pressure along with the time to obtain the change trend of the two-layer injection pressure and the actual injection amount along with the time, comparing the change trend with the injection allocation requirement and predicting the injection allocation measuring and adjusting period.

Compared with the prior art, the invention has the following technical effects:

the invention considers the pressure and flow relation of each position of a water distribution station, a water injection well mouth, a water injection well bottom water distributor and a water injection well reservoir in the layered water injection process, establishes a layered water injection well node analysis model which can be used for the analysis of a 2-layer to multi-layer layered water injection pressure system, and solves the model by adopting a step-by-step search method in a nonlinear equation set numerical solution method, compared with the traditional graphical method, the method can quickly solve when the number of layered layers is more than 2, and can theoretically solve an infinite layer, so the method has more superiority in the actual engineering calculation. And combining the node model with the separate injection measurement and regulation acquisition data to establish a prediction method of separate injection allocation error and separate injection measurement and regulation period, wherein the method can predict the separate injection allocation error, the injection allocation qualification rate and the measurement and regulation period of the separate injection, and the three parameters can be applied to effectively guide the separate injection process practice, such as: well selection basis of the layered water injection process, application limit of the layered water injection process, measurement and regulation early warning of the layered water injection process and the like. The invention provides corresponding theoretical basis for defining the characteristics and the law of the zonal injection of the low-permeability reservoir, and can obviously improve the zonal injection benefit.

Drawings

FIG. 1 is a schematic diagram of a pressure drop system in a zonal water injection well node analysis;

fig. 2 is a diagram showing a result of calculation of a dispensing cycle.

Detailed Description

The invention is further described below with reference to the accompanying drawings:

referring to fig. 1 to 2 of the drawings,

(1) layered water injection multi-layer node analysis model and solution thereof

The node analysis model embodies the flowThe mass and momentum of the fluid entering and exiting the node are conserved, and the pressure drop calculation of each section adopts a steady-state pipe flow and a steady-state seepage mathematical model. In the water injection well node analysis of the single-layer general system, the division of a pressure drop system comprises the following steps: pressure drop Deltap of ground horizontal pipe₁Pressure drop Δ p of underground vertical pipe₂Pressure drop Δ p of the mouth flow₃And the pressure drop Δ p of the injection water in the ground₄And fourthly, the method comprises the following steps. Wherein, the pipe flow pressure drop is calculated by Darcy formula, and the nozzle flow pressure drop is calculated by nozzle flow pressure drop model (divided into fixed nozzles and adjustable nozzles)^[10,17]And calculating, wherein the seepage pressure drop of the injected water under the ground is calculated by using a plane radial flow pressure drop model. The layered water injection well node model is established on the basis of a single-layer general water injection node model, and the pressure drop system division is characterized in that the flow pressure drop of a shaft pipe, the flow pressure drop of a nozzle and the seepage pressure drop are divided into a plurality of parts according to multiple layers, namely, the pressure drop is respectively delta p_2-1、…、△p_2-m，△p_3-1、…、△p_3-m，△p_4-1、△p_4-mAnd m is the number of layers of the separated layer water injection, as shown in figure 1.

The specific formula of each part of the pressure drop is as follows:

wherein Q is the amount of injected water, m³/d；L_pThe length of a water injection pipeline from a water distribution station to a wellhead is m; d_pIs the inner diameter of the water injection pipeline, m; a. the_pIs the internal cross-sectional area of the ground pipeline, m²；

In the formula, L_w、H_wWell depth and vertical depth, m, respectively; d_wIs the inner diameter of the oil pipe, m; a. the_wIs the internal cross-sectional area of the oil pipe, m²；λ_p、

λ_wThe coefficients of flow friction resistance in the ground pipeline and the oil pipe are respectively, and the method is dimensionless; the subscripts 1, m refer to the first and mth layers, respectively, m ═ 1,2，…，m_max；m_maxthe maximum number of layers for layered water injection is dimensionless.

In the formula D_nThe inner diameter of the water distribution nozzle is m; a. the_nFor distributing water nozzle overflow area, for adjustable-taste water nozzles, e.g. "U" shaped orifice, overflow area, m²；C_dFor adjusting the flow coefficient of the tap, C_d(x)＝-3.1004x⁴+8.7432x³-8.8037x²+3.64x +0.2635, dimensionless; x is the opening degree of the water nozzle, 0-1.0 and is dimensionless;

in the formula, h is the effective thickness of the reservoir, m; k_wIs water phase permeability, μm²；r_wIs the wellbore radius, m; r is_eThe water injection wave radius is m; s is epidermal factor, and is dimensionless; rho_wAs density of the aqueous phase, kg/m³；μ_wViscosity, mPa · s, of the injected water; b is_wThe volume coefficient of the injected water is dimensionless;

establishing a layered water injection node analysis model, taking the bottom hole flow pressure of the 1 st layer as a solution point, and using an inflow (pipe flow in a shaft) dynamic equation as shown in the formula, an outflow (seepage in a reservoir) dynamic equation of the 1 st layer and the 2 nd to the m th_maxAnd (3) forming a node analysis model of the multilayer separate injection water injection well by a layer outflow (seepage in a reservoir) dynamic equation and a relation between injection quantities of the plurality of layers, wherein the node analysis model is shown as a formula (5).

In the formula, p_jwf-inIs the bottom hole pressure of the inflow node, Pa; p is a radical of_jwf-out is the bottom hole pressure of the outflow node Pa; p is a radical of_rIs the formation pressure, MPa; .

For solving the node model, the traditional method adopts a graphical method, namely, an inflow dynamic curve and an outflow dynamic curve at a certain node are drawn, and the pressure and the flow corresponding to the intersection point of two lines are the injection pressure and the water injection quantity when the system balance is met. In the double-layer water injection node analysis model, the bottom hole node is one inflow and two outflow, so that the superposition of two outflow dynamic curves needs to be considered, the injection amount of an upper layer and a lower layer can not be determined, and the graphical method can not be actually solved in the node model during layered water injection.

In contrast, the solution of the node analysis model of the patent adopts a step-by-step search method in a nonlinear equation set numerical solution method. The principle is that firstly, a split coefficient (the ratio of the upper layer injection flow to the total injection flow) r of the injection amount is assumed_sfjAnd a total injection quantity Q of a value r_sfj∈(0，1),Q∈[0,1600]Then substituting into the upper layer outflow dynamic equation to calculate to obtain the total injection quantity and Q, and the upper layer injection quantity Q₁And injection pressure p_jwf1Then substituting the lower layer outflow dynamic equation to obtain the lower layer injection quantity Q₂And injection pressure p_jwf2And (4) trial calculation and search are carried out from small to large until the inflow pressure difference and the outflow pressure difference at the bottom hole node meet the requirement epsilon, and the calculation model is shown as a formula (6).

In the formula, Q_jM is the total dosage³/d；r_sf-mThe split coefficient of the injection quantity is distributed for the mth layer, and the dimension is not needed; epsilon is the maximum value of the inflow pressure difference and the outflow pressure difference of the bottom hole node of the first layer, and is MPa. The node analysis model adopts a step-by-step search method in a nonlinear equation set numerical solution method, is simpler, more convenient and faster, and is applied to the technical field of the analysis of the node analysis model>The multilayer dispensing of 2 layers is more advantageous.

(2) Prediction of injection allocation error and injection allocation qualified rate of stratified water injection

Under the condition that reservoir parameters and water injection technological parameters are determined, two-layer injection pressure and actual injection quantity under the working condition can be calculated through a separate injection water injection well node analysis model. And according to the definition of single well injection allocation error, [ design injection amount (last injection amount measured) -actual injection amount (last injection amount measured) ]/design injection amount (last injection amount measured), the injection allocation error can be predicted, and the expression is as follows:

E_Q＝[Q(t₂)-Q(t₁)]/Q(t₁) (7)

if only the formation pressure changes at two times, then there are:

[Q，Q₁，…，Q_m，p_jwf1，…，p_jwfm](t)＝f_w[ (fluid Property: p)_w,B_w,μ_w) (ground line: L)_p,ε_p,D_p) (wellbore 1: L)_w1,H_w1,ε_w,D_w,r_w) (wellbore 2: L)_w2,H_w2…, (shaft m: L)_wm,H_wm(water distribution nozzle 1: 2R)_n1,h_n1+2R_n1,x_n1) (water distribution nozzle 2: 2R)_n2,h_n2+2R_n2,x_n2) …, (water distribution nozzle m: 2R)_nm,h_nm+2R_nm,x_n2) (reservoir 1: h)₁,r_e1,p_r1(t),K_w1,s₁,p_ffB (reservoir 2: h)₂,r_e2,p_r2(t),K_w2,s₂) …, (reservoir m: h)_m,r_em,p_rm(t),K_wm,s_m) (Water injection Process: p)_j,Q_max)]. (8)

R_Q＝1-E_Q (9)

(3) prediction of testing and adjusting period of separated layer water injection

According to the descending trend of the formation pressure along with the time, the descending trend is substituted into a separate injection water injection well node analysis model, the change trend of the two-layer injection pressure and the actual injection amount along with the time can be calculated, and the appropriate injection allocation measuring and adjusting period can be predicted by comparing the change trend with the injection allocation requirement. The measured and adjusted cycle is defined as the time interval when the error of two measured and adjusted injections is larger than the requirement, and the expression is as follows:

[Q，Q₁，…，Q_m，p_jwf1，…，p_jwfm](t)＝f_z[ (fluid Property: p)_w,B_w,μ_w) (ground line: L)_p,ε_p,D_p) (wellbore 1: L)_w1,H_w1,ε_w,D_w,r_w) (wellbore 2: L)_w2,H_w2…, (shaft m: L)_wm,H_wm(water distribution nozzle 1: 2R)_n1,h_n1+2R_n1,x_n1) (water distribution nozzle 2: 2R)_n2,h_n2+2R_n2,x_n2) …, (water distribution nozzle m: 2R)_nm,h_nm+2R_nm,x_n2) (reservoir 1: h)₁,r_e1,p_r1(t),K_w1,s₁,p_ffB (reservoir 2: h)₂,r_e2,p_r2(t),K_w2,s₂) …, (reservoir m: h)_m,r_em,p_rm(t),K_wm,s_m) (Water injection Process: p)_j,Q_max)])]. (11)

On the basis of the prediction of the separate injection testing and debugging period, the classification of the testing and debugging wells and the early warning of the testing and debugging can be carried out, and the method comprises the following steps: reservoir parameters of water injection wells of the research block are substituted into a separate injection water injection well node analysis model, injection pressure and injection allocation quantity of each well can be obtained, the injection pressure and the injection allocation quantity are compared with the designed injection allocation quantity of the block, and therefore the wells which do not need to be measured and adjusted can be obtained, and the wells which need to be measured and adjusted can be measured and adjusted at any time, and therefore classification of the injection wells can be achieved, and measurement and early warning can be carried out.

Example 1 prediction of injection allocation error and injection allocation qualification rate of stratified injection

Example calculation is carried out, and the input known parameters are taken from data of L42-20 wells in G83 area of Changqing oil field, including L42-20 well pressure test result report, L42-20 well separate injection allocation test result report and G83 area length 4+5 length 6 oil deposit basic data, as shown in Table 1, wherein the opening degrees of water nozzles at two layers are all set to be 1.0, and the formation pressure of the water injection well can be increased along with time.

Table 1 known parameters

The results of the calculation of dispensing and injection allocation errors are shown in table 2:

TABLE 2 calculation of dispensing and filling errors

Example 2 prediction of stratified water injection trim cycles

Performing example calculation, wherein the input known parameters are shown in table 3, the opening degrees of the two-layer water nozzles are all set to be 1.0, and the fitting relation of the formation pressure and the time is assumed to be p_r＝p_r0+0.01t，E_{Q requirement}＝50％。

Table 3 known parameters

The results of the dispensing cycle calculation are shown in table 4 and fig. 2:

TABLE 4 calculation results of dispensing cycle

Therefore, the measured and adjusted period of the well at the moment is calculated to be 40-50 days.

Claims

1. a method for determining a period for measuring and adjusting the layered water injection of a tight oil reservoir, is characterized in that, comprises the following steps:

On the basis of the single-layer general water-injection node model, a multi-layer node analysis model for layered water injection is established;

Solve the multi-layer node analysis model of layered water injection until the pressure difference between the inflow and outflow at the bottom-hole node meets the required maximum value of the inflow and outflow pressure difference at the bottom-hole node of the first layer;

Through the multi-layer node analysis model of layered water injection, the injection pressure and actual injection volume of the two layers under this working condition are obtained. Predict the dispensing error;

According to the decreasing trend of formation pressure with time, it is substituted into the multi-layer node analysis model of layered water injection, and the variation trend of injection pressure and actual injection amount of two layers with time is obtained. .

2 . The method for determining the interval of water injection measurement and adjustment of layered water injection in a tight oil reservoir according to claim 1 , wherein, in the node analysis of the single layer general water injection well, the division of the pressure drop system comprises: the pressure drop of the surface horizontal pipe flow Δ p ₁ , the pressure drop of underground vertical pipe flow △p ₂ , the pressure drop of mouth flow △p ₃ and the seepage pressure drop of injected water in the ground △p ₄ ; The pressure drop is calculated by the nozzle flow pressure drop model, and the seepage pressure drop of the injected water in the ground is calculated by the plane radial flow pressure drop model; the difference between the pressure drop system division of the layered water injection well node model is the wellbore pipe flow pressure drop, the nozzle flow pressure The pressure drop and seepage pressure drop are divided into multiple parts according to the multi-layer, respectively △p _2-1 , …, △p _2-m , △p _3-1 , …, △p _3-m , △p _4-1 , △p _4-m , where m is the number of layers for layered water injection.

3. The method for determining the interval of water injection measurement and adjustment of a kind of layered water injection in a tight oil reservoir according to claim 2, is characterized in that, the concrete formula of pressure drop of each part is as follows:

In the formula, Q is the water injection volume, m ³ /d; L _p is the length of the surface pipeline, m; D _p is the inner diameter of the surface pipeline, m; A _p is the cross-sectional area of the surface pipeline, m ² ;

In the formula, L _w and H _w are the well depth and vertical depth, respectively, m; D _w is the inner diameter of the tubing, m; A _w is the cross-sectional area of the tubing, m ² ; λ _p and λ _w are the flow friction in the surface pipeline and the tubing, respectively. Resistivity coefficient, dimensionless; subscripts 1, m refer to the first layer and the mth layer respectively, m=1, 2, ..., m _max ; m _max is the maximum number of layers for stratified water injection, dimensionless;

In the formula, D _n is the inner diameter of the faucet, m; An _is the flow area of the faucet. For a seasonable faucet, such as a "U"-shaped orifice, the flow area is m ² ; C _d is the flow coefficient of the adjustable faucet , C _d (x)=-3.1004x ⁴ +8.7432x ³ -8.8037x ² +3.64x+0.2635, dimensionless; x is the opening of the faucet, 0-1.0, dimensionless;

In the formula, h is the effective thickness of the reservoir, m; K _w is the water permeability, μm ² ; r _w is the radius of the wellbore, m; r _e is the sweep radius of water injection, m; s is the skin factor, dimensionless; ρ _w is the density of the water phase, kg/m3; _μw is the viscosity of the water phase, mPa·s; _Bw is the volume coefficient of the water phase, dimensionless;

The establishment of the layered water injection node analysis model, taking the bottom hole flow pressure of the first layer as the solution point, the _inflow dynamic equation such as Eq. The relational expression of , together constitute the node analysis model of the multi-layer split injection water injection well, as shown in formula (5);

In the formula, p _jwf-in is the bottom hole pressure of the inflow node, Pa; p _jwf-out is the bottom hole pressure of the outflow node, Pa; _pr is the formation pressure, MPa.

4. A method for determining the interval of water injection measurement and adjustment of layered water injection in a tight oil reservoir according to claim 1, wherein the step-by-step search method in the numerical solution method of the nonlinear equation system is used to solve the problem, first assuming a splitting coefficient of the injection volume , the ratio of the upper layer injection flow to the total injection flow _rsfj and the total injection volume Q, its value rsfj∈(0,1),Q∈[0,1600], and then substitute it into the upper outflow dynamic equation to calculate, the total injection volume and Q , the injection volume Q ₁ of the upper layer and the injection pressure p _jwf1 , and then substituted into the dynamic equation of the lower layer outflow to obtain the injection volume Q ₂ and the injection pressure p _jwf2 of the lower layer. Until ε is required, the calculation model is shown in formula (6);

In the formula, Q _j is the total injection rate, m ³ /d; _rsf-m is the splitting coefficient of the injection rate in the m-th layer, dimensionless; ε is the required maximum value of the pressure difference between the inflow and outflow at the bottom-hole node of the first layer , MPa.

5. The method for determining the interval of water injection measurement and adjustment of a kind of layered water injection in a tight oil reservoir according to claim 1, characterized in that, the injection error is expressed as follows:

E _Q =[Q(t ₂ )-Q(t ₁ )]/Q(t ₁ ) (7)

If only the formation pressure changes at two moments, there are:

_[ _Q _, _Q ₁ _, _. _{_} _{_} _{_} D _p ), (wellbore 1: _Lw1 , _Hw1 , _εw , _Dw , _rw ),(wellbore 2: _Lw2 , _Hw2 ,),…,(wellbore m: _Lwm , _Hwm ,), (Water distribution nozzle 1:2R _n1 ,h _n1 +2R _n1 ,x _n1 ),(Water distribution nozzle 2:2R _n2 ,h _n2 +2R _n2 ,x _n2 ),…,(Water distribution nozzle m:2R _nm ,h _nm +2R _nm , x _n2 ), (reservoir 1: h ₁ , r _e1 , p _r1 (t), K _w1 , s ₁ , p _ff ,), (reservoir 2: h ₂ , r _e2 , p _r2 (t) , K _w2 , s ₂ ), …, (reservoir m: h _m , _rem , p _rm (t), K _wm , s _m ), (water injection process: p _j , Q _max )]; (8)

The calculation formula of the corresponding dispensing qualification rate is:

R _Q =1-E _Q (9).

6 . The method for determining the measurement and adjustment period of layered water injection in tight oil reservoirs according to claim 1 , wherein the measurement and adjustment period is defined as the time interval when the error of two measurement, adjustment and injection is greater than required, and the expression is as follows :

CY _Q =t _n -t ₁ , when E _Q =[Q(t _n )-Q(t ₁ )]/Q(t ₁ )<E _{Q requirement} , n=2,3,4,... ( 10)

_[ _Q _, _Q ₁ _, _. _{_} _{_} _{_} D _p ), (wellbore 1: _Lw1 , _Hw1 , _εw , _Dw , _rw ),(wellbore 2: _Lw2 , _Hw2 ,),…,(wellbore m: _Lwm , _Hwm ,), (Water distribution nozzle 1:2R _n1 ,h _n1 +2R _n1 ,x _n1 ),(Water distribution nozzle 2:2R _n2 ,h _n2 +2R _n2 ,x _n2 ),…,(Water distribution nozzle m:2R _nm ,h _nm +2R _nm , x _n2 ), (reservoir 1: h ₁ , r _e1 , p _r1 (t), K _w1 , s ₁ , p _ff ,), (reservoir 2: h ₂ , r _e2 , p _r2 (t) ,K _w2 ,s ₂ ),…,(reservoir m:h _m , _rem ,p _rm (t),K _wm ,s _m ),(water injection process:p _j ,Q _max )])];(11 ).

7. A method for determining a period of measurement and adjustment of layered water injection in a tight oil reservoir according to claim 1, wherein the designed injection volume is the injection volume measured in the previous measurement; the actual injection volume is the injection volume measured in the next measurement .

8. A system for determining a monitoring and adjusting period for layered water injection in a tight oil reservoir, characterized in that, based on the method for determining a monitoring and adjusting period for layered water injection in a tight oil reservoir according to any one of claims 1 to 7, comprising:

The model building module is used to establish a layered water injection multi-layer node analysis model on the basis of the single-layer general water injection node model;

The solution module is used to solve the multi-layer node analysis model of layered water injection until the inflow and outflow pressure difference at the bottom-hole node meets the required maximum value of the inflow and outflow pressure difference at the bottom-hole node of the first layer;

The allocation error prediction module is used to obtain the injection pressure and actual injection volume of the two layers under this working condition through the multi-layer node analysis model of layered water injection. Quantity/design allocation quantity, predict the allocation error;

The prediction module of the injection measurement and adjustment period is used to substitute the layered water injection multi-layer node analysis model according to the downward trend of the formation pressure with time to obtain the variation trend of the injection pressure and the actual injection volume of the two layers with time, and compare it with the injection volume. It is required to compare and predict the adjustment cycle of the annotation.